The present invention relates generally to assemblies for and methods of detecting the position of an object surface and more particularly to an optical probe assembly and method for automatically detecting the position of an object surface relative to a known reference, especially the position of a three-dimensional, curved surface such as the outer surface (or surfaces) of a contact lens or even the cornea of an eye.
For many years, the hard plastic lens has been the mainstay of the contact lens industry. Its rigid structure allows it to be formed into many designs with precise optical dimensions and often the wearer of hard lenses will gain better vision than with conventional spectacles. In spite of the convenience and cosmetic appeal of the lenses, many patients experience comfort problems which have led to the development of the more comfortable hydrogel (soft) lens. In the past few years the growth of soft lenses has averaged over twenty percent per year, compared to about two percent per year for hard lenses, a trend which is expected to continue through 1980.
The major problem confronting the contact lens practitioner is that often he is not able to accurately measure many of the physical dimensions and optical properties of the lens. This is particularly true of soft lenses which are more prone to manufacturing errors and, because of their flexibility, are difficult to inspect. Parameters of hard lenses, on the other hand, can be more quantitatively examined. However, several important parameters of each type of lens cannot be dimensionally verified, and these are often critical to the fit and comfort of the lens. This causes the practitioner considerable frustration in fitting new patients as well as in ordering a duplicate lens for patients who are accustomed to the fit of specific lenses. A slight deviation in one or more of the lense parameters is enough to cause patient eye irritation and/or discomfort. Without the equipment to accurately measure the lens, the practitioner often orders new lenses of different specifications when a prescription change is not actually needed. These problems have created an urgent need within the industry for a more complete and accurate inspection of contact lenses which can be made by lens laboratories as well as in the practitioner's office.
As will be seen hereinafter, the present invention is directed to an assembly and method for detecting the position of an object surface, especially the three dimensional surface or surfaces of a contact lens, utilizing a beam of light. In this regard, the prior art discloses a number of ways in which a beam of light interacts with the surface of an object in order to obtain certain information regarding the latter. This prior art includes the following United States Patents:
______________________________________ U.S. Pat. No. Inventor ______________________________________ 2,466,015 Ewing 3,589,815 Hosterman 3,782,827 Nisenson et al 3,794,429 Coeniger 3,822,096 Wilms et al 3,892,494 Baker et al 3,988,068 Sprague 3,994,589 Nodwell et al ______________________________________
Of these references, the most pertinent to the present invention appears to be the Ewing patent which is directed to a manually operated apparatus for locating reflecting surfaces and for measuring the curvatures thereof. While an apparatus of this general type is indeed capable of measuring the curvature of a surface, it is inherently limited by its manual method of operation to rather imprecise measurements and cannot be reliably used in measuring the surface curvatures of a contact lens or the like. On the other hand, as will be seen hereinafter, the automated assembly of the present invention and its method of operation, which are significantly different than the assemblies and methods disclosed in the above recited patents including Ewing, provide sufficiently precise and reliable measurements of the position of an object surface relative to a known reference for enabling it to be used in measuring the curvatures of a contact lens or even the cornea of an eye. Moreover, as will also be seen, the overall assembly of the present invention is uncomplicated in design, relatively economical to provide, and readily adaptable for different uses, especially its optical probe and scanning mechanism.